We have demonstrated improved survival of prematurely delivered rabbits following antenatal administration of aminophylline. We propose to study whether this effect is entirely secondary to antenatal acceleration of surfactant production or whether it in part is secondary to postnatal stimulation of respirations and/or ventilation. We will determine if the effect can be reproduced by administration of aminophylline shortly before premature delivery to pregnant rabbits following antenatal administration of saline or glucocorticoids. In this respect, we shall measure lung pressure-volume characteristics and phospholipid content of tracheal washes from animals killed before the first breath, and at 30 and 60 minutes of age in five groups of animals exposed antenatally to saline, glucocorticoids and aminophylline in varying combinations. In addition, we shall examine lungs from these animals histologically to look for differences in glycogen content, lipid content, osmiophilic granules and evidence of secreted surfactant in the various groups of animals. This study should permit us to determine if a study of aminophylline as a preventive agent for respiratory distress syndrome is warranted in the primate, both sub-human and human.